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Abstract Strigolactones are plant hormones with roles in a wide range of signaling and developmental processes. A yellow-striped maize mutant, (interveinalyellow)ivy, was determined to have low iron in tissues under normal growth conditions. The gene underlying theivymutation was mapped and identified asZmCCD8, a key enzyme in the biosynthesis of strigolactones. Under iron-replete conditions, comparison of the transcriptomes of wild-type plants and maizeccd8mutants revealed suppression of several iron-regulated genes inccd8. These genes are normally up-regulated during iron deficiency and include the key iron-regulated transcription factorIRO2as well as genes involved in the biosynthesis of iron chelators and transporters. External supply of synthetic strigolactone toivymutants alleviated chlorosis and returned iron-regulated gene expression to wild-type levels. In iron limited conditions, iron-regulated gene expression inccd8mutants responded normally, indicating that strigolactones are not required for response to externally imposed iron deficiency. However, they are required for basal expression of iron-regulated genes when adequate iron is available, highlighting a distinction between iron homeostasis during normal growth, and the iron deficiency response triggered by the lack of external available iron. The connection between strigolactones and iron homeostasis is not limited to maize, as Arabidopsisccd8mutants also show strong chlorosis when grown on medium with moderate levels of iron. This previously unappreciated role may have implications for the use of strigolactones in agricultural contexts.
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Ferroportin 3 is a dual‐targeted mitochondrial/chloroplast iron exporter necessary for iron homeostasis in Arabidopsis
Summary Mitochondria and chloroplasts are organelles with high iron demand that are particularly susceptible to iron‐induced oxidative stress. Despite the necessity of strict iron regulation in these organelles, much remains unknown about mitochondrial and chloroplast iron transport in plants. Here, we propose that Arabidopsis ferroportin 3 (FPN3) is an iron exporter that is dual‐targeted to mitochondria and chloroplasts.FPN3is expressed in shoots, regardless of iron conditions, but its transcripts accumulate under iron deficiency in roots.fpn3mutants cannot grow as well as the wild type under iron‐deficient conditions and their shoot iron levels are lower compared with the wild type. Analyses of iron homeostasis gene expression infpn3mutants and inductively coupled plasma mass spectrometry (ICP‐MS) measurements show that iron levels in the mitochondria and chloroplasts are increased relative to the wild type, consistent with the proposed role of FPN3 as a mitochondrial/plastid iron exporter. In iron‐deficientfpn3mutants, abnormal mitochondrial ultrastructure was observed, whereas chloroplast ultrastructure was not affected, implying that FPN3 plays a critical role in the mitochondria. Overall, our study suggests that FPN3 is essential for optimal iron homeostasis.
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- PAR ID:
- 10449520
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- The Plant Journal
- Volume:
- 107
- Issue:
- 1
- ISSN:
- 0960-7412
- Page Range / eLocation ID:
- p. 215-236
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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